Side rails are commonly used for tensioning and supporting screens in a screen deck. The side rails are removably attached to upright side walls or panels in the deck in a manner such that the rails engage a screen at its side edges and tension the screen in a secure manner.
Multiple vibrating screens are normally used, with a top screen separating the largest size of material, such as sand, gravel, crushed stone and the like with the material which passes through the top screen falling onto an intermediate screen. The intermediate screen separates an intermediate size of material, with the remainder falling through the intermediate screen onto a finer screen, which in turn separates the larger particles of those falling onto it and the smallest size falling through for collection beneath.
Different techniques have been utilized to removably attach the screen rails to the side walls or panels. For example, one very common technique involves the use of bolts or pins which extend through apertures in the screen rails and corresponding apertures in the side walls. A fastener is then used to secure the bolt or pin in place. The bolt or pin head is thus located on the side of screen rail which is exposed to the rock being screened or sorted.
The entire screen deck assembly is then vibrated, usually to produce a slow forward movement and a rapid rearward movement, so that the rock material will move forward with the screen but, due to inertia will permit the screen to move rearwardly under it. As a result, the rock material will work its way forwardly on the respective screen, so that material which does not fall through the screen will be discharged from the front of the respective screen, for collection.
The friction and abrasion resulting from the gravel and rock wearing on the screen rails eventually will wear the screen rails thin. The heads of the bolts used to secure the screen rails to the screen deck also can become worn down because of the abrasion of the gravels and rock moving on the screen in the deck.
Rubber-covered screen rails have been proposed for use in a screen deck, and this type of screen rail does exhibit greater useful life in a screen deck. However, special equipment must be used in order to manufacture such screen rails. Also, the cost of such screen rails is considerably greater than for conventional screen rails.
There has not heretofore been provided screen rails having extended wear life at a low cost.